Brake pad drag.

[Guest]

I need my memory refreshed as its been awhile since I've installed new pads. Should there be any appreciable drag as in the wheel will turn ok but will not spin freely? There are no weird noises or scoring of the disks, it all appears normal.

I didn't install the pads myself but they were freshly installed last Sept and there are only a few hundred Km on them.There is still a lot of material on them. I did, last week, install new ss brake lines and fresh fluid but I did not dissassemble or clean the calipers or the masters.

Now reading through the archives, I started to think that the return port in the master might be clogged and the test for that is to release pressure by opening a bleed nipple which I did. There was no change to this drag, indicating that it's not a hydraulic issue more a mechanical problem.

Before I rip into the calipers am I getting paranoid or is there something I should be concerned about?

Cheers.

[Agemax]

how "draggy" are they? can you turn the wheel by hand, or push the bike with no extra effort? if yes on those 2 i wouldn't worry.
if no on any of those 2 i would pull the calipers off and clean all the slidey bits and lube them up......

[AJ]

Which bike are these on? Single piston or opposed piston calipers? Are both pads dragging, or just one side?

So the question comes down to either the pistons aren't retracting enough or the caliper(s) won't center on the disc(s).

You can hit the caliper with a deadblow (or rubber) hammer on the piston, sliding it towards the disk, then tap it back lightly with from the inside to retract your piston. If that frees it up, pump the brake back up and see if the drag returns.

If the piston retracts fine and it's still dragging, it's not uncommon for people to fail to properly grease the slider pins, per Max's suggestion above. Synthetic brake grease recommended.

[eddie21]

I am watching this thread with great interest as I am having this issue as well. I've ridden 250km since installing new pads and they are still dragging. When I back up the bike the brakes squeal too. Before installing new pads these issues didn't exist. This is on a 1979 GS1000S.

[spyug]

This is on the new to me FZ with dual piston dual calipers. Knowing the state of the master cylinders and fluids when I was changing the brake lines I don't doubt now that parts were not properly greased, so I'll start there.

The wheel does turn but it requires a bit of force to overcome the inertia. It will not spin, unlike the back wheel that will, even with a chain and sprocket.

After seeing the crap job done, it is my intention to clean and rebuild the complete brake system but I don't, at present have the time and I'm trying to avoid more work.

I'll let you know what I find.

Thanks for the input.

[AJ]

Also note that these brakes do not have any mechanism to retract the piston(s) into the calipers. They rely on the slight imperfections of the disc surface to 'kick' the pads and push the pistons back. A tiny bit of drag is normal, although a lot of drag should NOT persist after you've ridden the bike. (AJ, who once worked on a brake drag detection system for a major automotive brake manufacturer that was developing low-drag brakes for improved fuel mileage.)

[Steve]

Also note that these brakes do not have any mechanism to retract the piston(s) into the calipers. They rely on the slight imperfections of the disc surface to 'kick' the pads and push the pistons back.

Besides the slight imperfections of the disc surface, they do also rely just a bit on the deformation of the square-section o-ring between the caliper and the piston. When pressure is applied, the o-ring deforms a bit as the piston is pushed out. When pressure is released, it straightens up, but that distance tends to be measured in thousandths of an inch, and precious FEW of them (maybe 1 or 2).

.

[AJ]

This is on the new to me FZ with dual piston dual calipers. Knowing the state of the master cylinders and fluids when I was changing the brake lines I don't doubt now that parts were not properly greased, so I'll start there.

The wheel does turn but it requires a bit of force to overcome the inertia. It will not spin, unlike the back wheel that will, even with a chain and sprocket.

After seeing the crap job done, it is my intention to clean and rebuild the complete brake system but I don't, at present have the time and I'm trying to avoid more work.

I'll let you know what I find.

Thanks for the input.

(EDIT: I just caught that the FZ is a 1985 FZ, not a modern one. My response below probably does not apply, but still something that might apply to somebody someday.)

Ohhhh, the FZ. You don't have a speedo drive on the front wheel, do you? (it's a takeoff on the countershaft sprocket, right?)

I once installed a new front tire on my Busa and the brakes dragged terribly. They wouldn't free up even when banged with a deadblow mallet. A little research and I discovered that I had mounted the tire backwards and flipped the wheel. It looks the same from either side and the rotation mark is very subtle. But it is not symmetric side-to-side, just off by x thousandths. I remounted the tire (%&$#!), reinstalled the wheel correctly, and all was good. Just a thought.

[AJ]

Besides the slight imperfections of the disc surface, they do also rely just a bit on the deformation of the square-section o-ring between the caliper and the piston. When pressure is applied, the o-ring deforms a bit as the piston is pushed out. When pressure is released, it straightens up, but that distance tends to be measured in thousandths of an inch, and precious FEW of them (maybe 1 or 2).

.

You are correct, sir! The brakes I was working on actually had special springs to move the pads back quite further, but you are right about the o-rings. Bravo!

[Agemax]

i had problems a while back where the pads were too thick compared to the originals, so the pistons weren't retracting far enough to allow the pads to lose the grip on the discs.
the pads are a b1tch to sand or file back, so i had to remove some of the material that was on the pistons. worked fine after that

[spyug]

Thanks guys. My next move, tomorrow, will be to pull the calipers and have a look at the bits and pieces. I'm thinking that a) the pads are too thick or b) the parts have not been properly greased maybe even c) a combination of both.

I'll let you know what I find.

[eil]

Dunno about the FZ ones, but most calipers are fairly easy to disassemble, inspect, and reassemble. On a bike that's new to me, I'd do it even if they seemed to work fine!

[spyug]

On a bike that's new to me, I'd do it even if they seemed to work fine!

You know I generally do as well but I was led to believe (with documentation from the "professional" shop that did the work) these brakes had been cleaned and rebuilt last Sept, less than 600Km ago. Only when I got to changing the brake hoses did I realise nothing had been done other than swapping of pads. The one time I break my rule and I get caught out.

That won't happen again.

[spyug]

Well, true to form, the right caliper is fudged. One piston is stuck and doesn't move at all and is holding the pad tight to the disk. I was able to get the other piston out with compressed air but this one doesn't budge. I've split the caliper and once I figure out how to block the transfer ports, I try more air or possibly a grease gun. I've used both methods with about equal success.

The piston that came out was not too bad and cleaned up nicely but there was quite a bit of gunge around the seals. The seals themselves look ok once cleaned but i'll replace them.

So note to self, "Always check the calipers on new to you bikes".

I'll let you know how this goes.

Spyug

[AJ]

Well, true to form, the right caliper is fudged. One piston is stuck and doesn't move at all and is holding the pad tight to the disk. I was able to get the other piston out with compressed air but this one doesn't budge. I've split the caliper and once I figure out how to block the transfer ports, I try more air or possibly a grease gun. I've used both methods with about equal success.

The piston that came out was not too bad and cleaned up nicely but there was quite a bit of gunge around the seals. The seals themselves look ok once cleaned but i'll replace them.

So note to self, "Always check the calipers on new to you bikes".

I'll let you know how this goes.

Spyug

Sometimes the simplest answer is the correct answer, even if the "evidence" (your shop receipt) indicates otherwise. At least you now have a clear path to salvation.

That old FZ should be a fun bike when you're done with it. A riding buddy of mine had one in the early 1990's as we ripped through northwest Jersey together.